Secondary lithium ion batteries now power most portable electronic devices, but lithium is highly flammable and lithium ion batteries need replacement more frequently than is ordinarily desirable. Many alternate battery chemistries and designs have been proposed, but they have inherent shortcomings.
Conventional alkaline batteries have been in use for many years. Alkaline batteries have reasonable energy densities, but they are difficult to recharge once fully discharged, due to zinc crossover during discharge and hydrogen formation during the recharging process.
In Lin et al., Science, 349, Issue 6255, pp. 1529-1532 (2015), a new battery is described with chemistry that avoids hydrogen formation. Lin's battery is limited, however, by the use of a separator membrane that has high resistance (approximately 0.895 ohm-cm2 at room temperature).
In Parker et al., Science 356, Issue 6336, pp. 415-418 (2017), a new battery is described that can be discharged to 40% capacity and recharged. However, zinc crossover occurs at higher discharge, limiting performance.